Process for inhibiting corrosion



liquids or in protecting certain metals. tration, chromates are not useful in aqueous alcohol solu- United States Patent 3,234,144 PROCESS FOR INHIBITING CORROSION Edward L. Morehouse, Snyder, N.Y., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Mar. 26, 1962, Ser. No. 182,614 13 Claims. (Cl. 252389) This application is" a continuation-in-part of application Serial No. 777,561, filed December 2, 1958, now abandoned.

This invention relates to a process for retarding corrosion that involves employing organosilicon compounds as corrosion inhibitors.

The corrosion of metals that are in contact with static or moving water is a widespread problem that is encountered in a variety of industrial processes (e.g. such processes as the removal of scale from metal surfaces using acid solutions which may attack the base metal) and-in a variety of industrial apparatus (e.g. boilers, cooling systems and liquid storage tanks).

Hence, a wide variety of inhibitors (i.e. compounds that retard the corrosion of metals) have been added to water that comes in contact with metals in order to reduce the corrosion of the metals. Such known inhibitors include both organic materials and inorganic materials. Illustrative of the organic materials that have been used as inhibitors are: guanidine, colloids, citrates, coal tar derivatives, petroleum bases, thiocyanates, peptones, phenols, thioureas, tannin, quinoline, morpholine, triethanolamine, tartrates, glycol mono-ricinoleate, organic nitrites, amines, mercaptans, sulfonated hydrocarbons, fatty oils, organic oils and soaps. Illustrative of the inorganic materials that have been used as inhibitors are: sulfates, sulfides, fluorides, hydrogen peroxide and the alkali metal chromates, nitrites, phosphates, borates, tungstates, molybdates, carbonates and silicates.- Although the above-mentioned inhibitors have been found useful in some instances, they suffer from various disadvantages that limit the scope of their utility.

Thus, some known inhibitors are useful only in certain By way of illustions because they promote the decomposition of the alcohol. As a further illustration, organic amines although useful as inhibitors for ferrous metals, promote the corrosion of copper and copper alloys.

Furthermore, water that contains known inhibitors often attacks organic materials with which it comes into contact (e.g. inhibited coolants in internal combustion engines sometimes attack the rubber hoses that form part of the cooling system) or retains its non-corrosive properties only over a narrow temperature range or foams excessively.

It is an object of this invention to provide an improved process for inhibiting the corrosion of metals that come in contact with water which is generally applicable to the protection of all of the metals used in industrial processes and apparatus.

Another object of this invention is to provide an improved process for inhibiting the corrosion of metals that come in contact with water which is generally applicable to bothpure water and solutions containing water and water-soluble organic or inorganic compounds.

Other objects of this invention are to provide an improved process for inhibiting the corrosion of metals that come in contact with Water which does not entail attack on organic materials (e.g. rubber) by the inhibited water, or the loss of the non-corrosive properties of the inhibited water outside a narrow temperature range or excessive foaming of the water.

This invention provides an improved process for inhib- "ice iting the corrosion of metals that come in contact with water which involves adding to the water, as an inhibitor, an organosilicon compound containing an amino group linked to a silicon atom by a divalent hydrocarbon group containing at least three carbon atoms wherein the amino group is attached to at least the third carbon removed from the silicon atom.

The organosilicon inhibitors that are used in this invention are compounds, including both hydrocarbonoxysilanes (including alkoxysilanes and aroxysilanes) and siloxanes (including homopolymeric and copolymeric siloxanes), containing an amino group that is linked to a silicon atom through a divalent hydrocarbon group containing at least three carbon atoms wherein the amino group is attached to at least the third carbon removed from the silicon atoms. As used herein hydrocarbonoxy denotes a monovalent group composed of a monovalent hydrocarbon group linked to an oxygen atom (e.g.. an OR groupwhere R is a monovalent hydrocarbon group). These organosilicon inhibitors can be primary, secondary or tertiary amines, but they are preferably primary amines. These organosilicon inhibitors contain the group that is represented by the formula:

wherein R is a divalent hydrocarbon containing at least three successive carbon atoms; the Z N group is attached to at least the third carbon removed from the silicon atom; Z is a hydrogen atom, an unsubstituted or a substituted monovalent hydrocarbon group, or a divaient group that is derived from an oXirane compound by the opening of the oxirane ring and that connects the nitrogen atom to the silicon atoms by a carbon to carbon to oxygen linkage; and the free valences of silicon link the silicon atom to at least one alkoxy or aroxy group (i.e. when the As used herein an oxirane compound is a compound containing at least one oxirane ring structure, i.e. a structure represented by the formula:

Typical of the groups represented by R in Formula 1 are: (a) groups containing an arylene group linked to an alkylene group (e.g. where Formula 1 represents the group l NArC l-l siz wherein a has a value from 1 to 4 an Ar is an aryl group, preferably a phenyl group); (b) groups containing an alkylene group linked to an arylene group (e.g. where Formula 1 represents the group Z NCH C H SiE); (c) alkylene groups (e.g. Where Formula 1 represents the group Z Nc H Sia= wherein n R OOCR wherein R is an alkylene group containing at least two, and preferably from 2 to 10, carbon atoms such as the ethylene, 1,3-propylene and 1,4-butylene groups and R is a monovalent hydrocarbon group such as defined above for Z); (d) a divalent group that is derived from an oxirane compound by the opening of the oxirane ring which connects the nitrogen atom and the silicon atom in Formula 1 through a carbon to carbon to oxygen linkage, that is composed only of carbon, hydrogen and OX oxygen, and that is linked to the nitrogen atom of Formula l by a carbon to nitrogen bond and to the silicon atom of Formula 1 by an oxygen to silicon bond to provide a cyclic structure (i.e. a group denoted hereinafter as an OR group where R is a divalent hydrocarbon or a divalent hydrocarbonoxy-hydrocarbon group); and (e) a hydroxyl-substituted monovalent group derived from an oxirane compound by the opening of the oxirane ring (denoted hereinafter as an HOR group). The monovalent hydrocarbon groups represented by Z in Formula 1 preferably contain from 1 to 10 carbon atoms. In Formula 1, Z may be the same or different.

Silanes that are useful as inhibitors in this invention contain the group that is represented by Formula 1 and may be more specifically depicted by Formula 2.

wherein R is a monovalent hydrocarbon group or a NI-I C I-I group, X is an alkoxy group (such as a methoxy or ethoxy group) or an aroxy group (such as a phenoxy group), b has a value of from 0 to 2, n, R and Z have the above-defined meanings, f has a value from O to 2 and represents the number of the above-defined divalent groups represented by Z, (3b-f) has a value from 1 to 3, and Z is preferably a hydrogen atom. Illustrative of the monovalent hydrocarbon groups represented by R in Formula 2 are the alkyl groups (eg the methyl, ethyl, propyl and butyl groups), the aryl groups {c.g. the phenyl group) and the aralkyl groups (e.g. the betaphenylethyl group). The monovalent hydrocarbon groups represented by R preferably contain from 1 to carbon atoms.

Illustrative of the preferred silanes represented by Formula 2 (i.e. where both groups represented by Z are hydrogen atoms) are gamma-aminopropyltriethoxysilane, gamma aminopropyltripropoxysilano, gamma aminopropyl (methyl) diethoxysilane, gamma-aminopropyl ethyl diethoxysilane, gamma-aminopropyl (ethyl diethoxysilane, gamma-aminopropyl(phenyl)diethoxy silane, deltaaminobutyltriethoxysilane, delta-aminobutyl (methyl diethoxysilane, delta-arninobutyl(ethyDdiethoxysilane, deltaaminobutyl(phenyl)diethoxysilane and epsilon-aminopentyltriethoxysilane. Illustrative of the silanes represented by Formula 2 where at least one group represented by Z is a group derived from an epoxy compound (i.e. the above-defined OR and HOR groups) are those silanes produced by reacting one mole of gammaaminopropyltriethoxysilane and one or two moles of a hydrocarbon compound containing at least one oxirane ring (e.g. ethylene oxide, 1,2-propylene oxide, styrene oxide and dipentene dioxide) or a hydroearbonoxy-hydrocarbon compound containing at least one oxirane ring (eg. l,2-epoxy-3-isopropoxy-propane and phenyl glycidyl ether). illustrative of the silanes represented by Formula 2 wherein at least one group represented by Z is a monovalent hydrocarbon group, are N-methyl-gammaaminopropyltriethoxysilane, N,N-dimethyl-gamma-aminopropyltriethoxysilane, and N-N-dimethyl delta aminobutyl(methyl)diethoxysilane. Illustrative of the silanes represented by Formula 2 where Z is an alkyl group containing an amino substituent (i.e. the above-defined NH R group) are N-gamma-aminopropyl-delta-aminobutyltriethoxysilane and N beta aminoethyl gammaaminopropyltriethoxysilane. Illustrative of the silanes represented by Formula 2 where one group represented by Z is an alkyl group containing a hydroxyl substituent (i.e. the above-identified HOR group) are N-betahydroxylethyl gamma aminopropyltriethoxysilane, N- beta hydroxyethyl delta aminobutyl(methyl)diethoxysilane. Illustrative of the silanes represented by Formula 2 where Z represents an alkyl group containing a cyanosubstituent group (i.e. the above-defined NCR group) are N beta cyanoethyl gamma aminopropyltriethoxysilane N beta-cyanoethyl delta aminobutyltriethoxysilane and N-beta-cyanoethyl-delta-aminobutyl(methyl) diethoxysilane. Illustrative of the silanes represented by Formula 2 where Z represents an alkyl group containing an ester su-bstituent group (i.e. the above-defined R OOCR group) are N-beta-carbethoxyethyl-gammaaminopropyltriethoxysilane, N beta carbethoxyethyldelta aminobutyl(methyl)diethoxysilane and N,N dicarbethoxyethyl gamma aminopropyltriethoxysilane. Illustrative of the silanes represented by Formula 2 where R is an arylene group are p-aminophenyltriethoxysilane and m-aminophenyltriethoxysilane. Illustrative of silanes represented by Formula 2 wherein R is an arylene group linked to an alkylene group are beta-(p-aminophe'nyl) ethyltriethoxysilane, p aminophenylmethyltriethoxysilane, beta p aininophenylethyl(methyl)diethoxysilane, beta- (aminophenyl -ethyldimethylethoxysilane, betaaminotolyl)-ethyltriethoxysilane and p-aminophenylmethyltriethoxysilane. Illustrative of silanes represented by Formula 2 wherein R is an alkylene group linked to an arylene group are metaand para-aminomethylphenyltriethoxysilane. Illustrative of silanes represented by Formula 2 wherein R is a NH C I-I group are bis(gammaaminopropyl)diethoxysilane, delta amino beta methylbutyl epsilon-aminopentyldiethoxysilane (i.e.

H NCH CH CH (CI-I CH Si OC H 2 CH NH and bis delta-aminobutyl diethoxysilane.

Siloxanes that are useful as inhibitors in this invention contain the group that is represented by Formula 1 and may be more specifically described as containing one or more of the siloxane groups represented by Formula 3.

wherein R, R and b have the above-defined meanings and Z has the meanings defined above for Z other than the -OR group. In Formula 3, Z is preferably a hydrogen atom. Illustrative of the preferred siloxane groups represented by Formula 3 (i.e. where both groups represented by Z are hydrogen atoms) are the beta- (aminophenyl)ethylsiloxy, beta (aminotolyl) propylsiloxy, gamma aminopropylsiloxy, gamma aminopropyl (methyl)siloxy, gamma-aminopropyldimethylsiloxy, deltaaminobutylsiloxy, delta-aminobutyl(methyl)siloxy, delta aminobutyldimethylsiloxy, epsilon aminopentylsiloxy groups and the like. Illustrative of the siloxane groupsrepresented by Formula 3, wherein at least one group represented by Z is a group derived from an epoxy compound (i.e. the above-defined HOR group) are the siloxane groups derived by reacting one mole of a siloxane containing one gamma-aminopropylsiioxy or delta-aminobutylsiloxy group and one or two moles of a hydrocarbon compound containing at least one oxirane ring (e.g. ethylene oxide, 1,2-propylene oxide, styrene oxide and dipentene dioxide) or a hydrocarbonoxy-hydrocarbon compound containing at least one oxirane ring (e.g. 1,2-epoxy- 3-isopropoxy-propane and phenyl glycidyl ether). Iilustrative of the siloxane groups represented by Formula 3 where at least one group represented by Z is a monovalent hydrocarbon group are the N-methyl-gammaaminopropylmethylsiloxy, N,N dimethyl delta aminobutyl(methyl)siloxy, and N,N-dimethyl-gamma-aminopropylsiloxy groups. Illustrative of the siloxane groups represented by Formula 3 where one of the groups represented by Z is an amino-substituted alkyl group (i.e. the above-defined H NR group) are the N-beta-arninoethyl gamma aminopropyl(methyl)siloxy, N gamma- 'siloxy and meta-amniophenylsiloxy groups.

aminopropyl-delta-aminobutylsiloxy and N-beta-aminoethyl delta aminobutylmethylsiloxy groups. Illustrative of the siloxane groups represented by Formula 3 where one of the groups represented by Z is a hydroxylsubstituted alkyl group (i.e. the above-defined HOR group) are N beta-hydroxyethyl delta aminobutyl (methyl)siloxy and N ,N di(beta hydroxyethyl) deltaaminobutyl(methyl)siloxy groups. Illustrative of the siloxane groups represented by Formula 3 where Z represents a cyano-substituted alkyl group (i.e. the abovedefined NCR group) are N-beta-cyanoethyl-gammaaminopropyl(methyl)siloxy, N beta cyanoethyl deltaaminobutylsiloxy, and N beta cyanoethyl delta-aminobutyl(methyl)siloxy groups. Illustrative of the siloxane groups represented by Formula 3 where Z represents an alkyl group containing an ester substituent group (i.e. the above-defined R OOCR group) are the N-beta-carbethoXyethyl-gamma-aminopropyl(methyl)siloxy, N ,N-dicarbethoXyethyl-gamma-aminopropylsiloxy and N-betacarbethoxyethyl-delta-aminobutyl (methyl) siloxy groups. Illustrative of siloxane groups represented by Formula 3 where R is an arylene group are the para-aminophenyl- Illustrative of siloxane groups represented by Formula 3 where R is an arylene group linked to an alkylene group are the beta- -aminophenyI)ethylsiloxy, beta-(p-aminophenyl)ethyl (methyl) siloxy, beta- (p-arninophenyl ethyldimethylsiloxy, beta-(p-aminotolyl)ethylsiloxy and p-aminophenylmethyldimethylsiloxy groups. Illustrative of solioxane groups represented by Formula 3 where R is an alkylene group linked to an arylene group are the metaand para-aminoethylphenylsiloxy groups. Illustrative of the siloxane groups represented by Formula 3 wherein R is a esses for their production are disclosed in U.S. patent applications Serial Nos. 615,480, filed October 12, 1956, and

- now abandoned; 655,506, filed April 29, 1957, and now abandoned; 615,463, filed October 12, 1956, and now abandoned; 727,527, filed April 10, 1958, and now aban- V doned; 668,621, filed June 28, 1957, now U.S. Patent No.

2,907,784, and 727,534, filed April 10, 1958, and now abandoned.

Organosilicon inhibitors containing the group can be produced by reducing compounds containing the NCC H SiE group. By way of illustration, p-aminomethylphenyltriethoxysilane can be produced by forming a mixture of p-cyanophenyltriethoxysilane dis solved in toluene, hydrogen and a catalytic amount of nickel supported on alumina and heating the mixture to a temperature of about 150 C. to cause the p-cyanophenyltriethoxysilane and the hydrogen to react to produce para-aininomethylphenyltriethoxysilane.

. Organosilicon compounds containing a group represented by Formula 1 where one of the free valences of silicon atom is attached to a H NC l-I group can be I produced by processes that include reducing the corresponding cyauo compounds. Thus, organosilicon compounds containing two aminoalkyl groups attached to the same silicon atom can be produced by known reducing processes employing, as starting materials, organosilicon compounds containing two cyanoalkyl groups attached to the same silicon atom. Suitable starting organosilicon compounds containing two cyanoalkyl groups attached to the same silicon atom and processes for their production .has a value from 1 to 3.

6 are disclosed in United States patent applications Serial Nos. 555,203, filed December 23, 1955, and now abandoned, and 555,208, filed December 23, 1955, now U.S. Patent No. 2,908,700.

Silox-anes that are useful as inhibitors in this invention includes homopolymeric compounds containing only one type of siloxane group represented by Formula 1 (or more specifically by Formula 3). Useful siloxanes also include copolymeric compounds that contain: (a) two or more types of siloxane groups represented by Formula 3; or (b) one or more of the latter-mentioned siloxane groups and also one or more siloxane groups represented by the formula:

wherein R is a monovalent hydrocarbon group and e Illustrative of the monovalent hydrocarbon groups represented by R in Formula 4 are the alkyl groups (e.g. the methyl, ethyl, propyl and butyl group), the aryl groups (e.g. the phenyl group),

the aralkyl groups (e.g. the phenylethyl group), the

alkenyl groups (e.g. the vinyl and the allyl groups), the cyclo alkenyl (e.g. the cyclohexenyl group), and the cycloalkyl groups (e.g. the cyclohexyl group). Prefer ably, these monovalent hydrocarbon groups contain up to ten carbon atoms. Illustrative of the groups represented by Formula 4 are the methylsiloxy, dimethylsiloxy, trimethylsiloxy, ethyl(vinyl)siloxy, beta-phenylethylsiloxy, diphenylsiloxy, phenyl(ethyl)methylsiloxy and diethylsiloxy groups.

The siloxanes that are useful in this invention as inhibitors can have a linear, cyclic or crosslinked structure or combination of these structures.

The siloxanes can contain alkoxy or hydroxyl groups bonded to silicon and SiO groups.

Illustrative of the siloxane homopolymers that are useful as inhibitors in this invention are gamma-amino propyl(methyl)siloxane cyclic trimer and tetramer, deltaaminobutyl(methyl)siloxane cyclic trirner and tetramer, linear hydroxy end-blocked delta-aminobutyl(rnethyl) polysiloxanes, gamma aminopropylpolysiloxanes, bis (delta aminobutyl)tetramethyldisiloxane, and deltaaminobutylpolysiloxane.

Illustrative of the siloxane copolymers that are useful as inhibitors in this invention are bis(trimethylsiloxy) gamma-aminopropyl(methyl)trisiloxane, copolymers containing dimethylsiloxy and gamma-aminopropyl(methyl) siloxy or delta-aminobutyl(methyl)siloxy groups, copolymers containing gamma-aminopropylsiloxy and phenylsiloxy, methylsiloxy or vinylsiloxy groups, copolyrners containing delta-aminobutyl siloxy and phenylsiloxy groups of amylsiloxy groups, copolymers containing N,N- di(beta-hydroxyethyl) delta aminobutyl(methyl)siloxy and dimethylsiloxy groups.

These useful copolymeric inhibitors can be produced by the cohydrolysis and co-condensation of silanes represented by Formula 2 and silanes represent by the formula:

wherein R and e have the meanings defined for Equation 4 and X has the meaning defined for Equation 2. Illustrative of silanes represented by Formula 5 are methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, phenyltriethoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, amyltriethoxysilane, ethylvinyldiethoxysilane, diethyldiethoxysilane and diphenyldiethoxysilane.

Preferably, the organosilicon inhibitors contain an amino group to silicon atom ratio of at least 1:25 and most desirably from 1:2 to 2:1. These organosilicon inhibitors, as contrasted with other organosilicon compounds, were found to be characterized by their greater solubility in alcohols, especially ethanol. The solubility of these inhibitors is at least about 1 part by weight per 100 parts by Weight of ethanol but the most useful inhibitors are soluble to the extent of about 10 parts by weight per 100 parts by weight of ethanol.

The amount of the organosilicon compound used as an inhibitor in this invention will vary widely from case to case depending upon the temperature, the type of metal or metals in contact with the water, the pH of the water, the velocity of the water, solutes or other materials in the water, and prior treatment or corrosion of the metal and the specific results desired. In general, amounts of the organosilicon inhibitor of from .0001 part to 10 parts by weight per 100 parts by weight of the liquid are useful but amounts of the organosilicon inhibitor from 0.001 part of 3.0 parts by Weight per 100 parts by weight of the liquid are preferred. The above ranges are given to indicate the generally useful and preferred amounts of the organosilicon inhibitor and may be departed from, though it is not usually desirable to do so since no advantage is gained thereby.

In the practice of this invention the organosilicon inhibitor is added to water or an aqueous solution and, for best results, the inhibitor is then uniformly dispersed throughout the water or the solution. Any suitable means can be used to disperse the inhibitor throughout the water or the solution. Thus, in the case of moving liquids that are in contact with the metal to be protected, the in hibitor employed in this invention can be added to the liquid while the liquid is in use and dispersion of the inhibitor throughout the liquid is achieved by the movement of the liquid. However, the inhibitor can be added to the liquid (prior to the use of the liquid in contact with the metal to be protected) and the inhibitor can be dispersed throughout the liquid by stirring the liquid. This latter procedure is preferred where the liquid is to be stored or where the liquid undergoes little movement when in use.

This invention is generally applicable to liquids that contain water. Suitable liquids are pure water, aqueous solutions containing inorganic solutes and solutions containing water and water soluble organic compounds, especially water soluble organic liquids. illustrative of suitable aqueous solutions containing inorganic solutes are aqueous sodium and calcium chloride refrigerating solutions, acidified pickling solutions (e.g. aqueous sulfuric acid solution), corrosive well water or river water containing chlorides, carbonates and sulfates which may be used as process water in industry, and the like. Illustrative of suitable solutions containing water and a Water soluble organic liquid are solutions containing water and monohydric or polyhydric alcohols (eg. methanol, ethanol, propanol, ethylene glycol, propylene glycol and glycerol), hydroxyl and alkoxy end-blocked polyallzylene oxides (such as polyethylene oxide), sulfoxides (such as methyl sulfoxide), formamides (such as dimethyl formarnide) or cyclic ethers free of olefinic unsaturation (such as tetrahydrofuran and dioxane) or the like. Suitable solutions containing water and a water soluble organic liquid should contain at least 0.1 part by weight, or preferably at least 5 .0 parts by Weight of water per 100 parts by weight of the water and the organic liquid.

This invention is generally applicable to the protection of all metals and alloys that are suitable for use in industrial processes and apparatus. Metals whose corrosion is retarded by the process of this invention include magnesium and the metals below magnesium in the electromotive series (e.g. aluminum, copper, chromium, iron, manganese, nickel, lead, silver, tin, beryllium and zinc) as well as alloys of such metals (e.g. brass, bronze, solder alloys, steel and the like). This invention is particularly applicable to the protection of brass, iron, copper and aluminum.

Compared with known processes for preventing corrosion of metals that are in contact with water, this invention provides numerous advantages. Thus, the inhibitors used in this invention can be added to a Wide variety of aqueous solutions and inhibit the corrosion of a wide variety of metals. In addition, the inhibitors used in this invention are effective over a wide temperature range and these inhibitors do not cause the liquids in which they are employed to foam excessively. Furthermore, these inhibitors do not promote the decomposition of organic compounds present in the water nor do they attack organic materials with which the water may come .into contact.

This invention is applicable to preventing the corrosion of metals that are cleaned by acid solutions or that are used in cooling coils, boilers, refrigeration and air conditioning equipment, heat exchange tubes, storage tanks for liquids, pipes, solvent containers, tank cars, ballast tanks containing sea water, and the like. This invention is particularly applicable to inhibiting the corrosion of the cooling systems of internal combustion engines in contact with aqueous alcohol anti-freeze compositions. h

The improvements in corrosion inhibition resulting from the practice of the present invention were found and evaluated by both simple visual observations of corrosion in beaker tests and also more elaborate laboratory tests designed to simulate field conditions. In the examples given below, both types of evaluation tests were employed.

SHORT-TERM TESTS AT ROOM TEMPERATURE This is a simple test for visual observation of corrosion on test specimens. The test specimen, comprising a metal strip which has been cleaned by scouring with ordinary household cleanser, flushed and dried, is immersed into an inhibitor-containing test liquid in a beaker. The liquid is aerated vigorously for twenty four (24) hours at room temperature. A control sample using a strip of similar metal in a similar liquid containing no inhibitor is run simultaneously. The extent of rusting is then noted and :1 corrosion rating is given on the scale: (A is nil or a trace amount of corrosion, B is small amount of corrosion, C is medium amount of corrosion and D is large amount of corrosion.

ZOO-HOUR CORRGSION TEST This is a laboratory test of corrosion inhibitors. This test has proven over many years of use to be useful in evaluating inhibitors for use in water and aqueous alcohol anti-freeze solutions in hydraulic and heat transfer applications. The test involves immersing clear strips of metal (usually iron, aluminum, brass and copper) and a brass coupon on which is a spot of solder, composed of 50 wt.- percent lead and 50 wt.-percent tin, in the test fluid with heating and aeration for a period of 200 hours. After this exposure, the specimens are cleaned and corrosion of the metal strips is measured by weight loss in milligrams. The corrosion of the spot of solder 0n the brass coupon is given a rating (called solder spot rating, abbreviated SS in the examples) by visual inspection with a rating of 6 indicating little or no corrosion and a rating of 0 indicating very severe corrosion.

Each test unit consists of a 600 ml. glass beaker equipped with a reflux condenser and aeration tube. The test specimens are cut from inch sheet stock usually with a total surface area of about nine (9) square inches. Test temperature is 180 F. and the aeration rate is 0.028 cubic foot per minute. Specimens are separated with Z-shaped glass rods and are covered with 350 cc. of solution. Except Where otherwise indicated, water used in preparing test solutions has parts per million added of each of bicarbonate, chloride, and sulfate ions. This gives an accelerated corrosion rate and is nearly equivalent to conditions encountered in actual practice. Duplicate tests are run simultaneously, and both values on the average values of weight loss, final pH and final RA (defined below) are given.

The reserve alkalinity of an alcohol-containing aqueous anti-freeze composition is a measure of the ability of the composition to resist a decrease in pl l due to the presthe test conducted as described above.

' tested and results obtained are set forth in Table II be- 9 10 ence of acidic materials. Reserve alkalinity (abbreviated I t TABLE II Ratin RA in the examples) is determined by titrating a sam- 6 b fl th th e i ple (about cc.) of the composition with 0.1 aqueous i F 1 n A hydrochloric solution. From the number of milliliters of G Q 11 3! 1 OXKSII ane l l the acid actually required to neutralize the sample, the 5 aimma'ammopropy met y cyc 1c S1 oxanes (mlx A number that would be required to neutralize 100 milliliters G we) th th A of the composition if it contained a water to alcohol ratio i m 2 oxysl ane A of 3 :1 on a volume basis is computed and this latter nurn- 9 me oxysl f "7 her is the reserve alkalinity of the composition. B13 (tnmethylslloxy) gamma'ammopropylmethyl d as an abbreviaane 7-, 7 i g fi g examples BR use 10 A copolymer containing 80 parts by welght of deltat th Se t-nvention. armnobutylmethylsiloxy groups and parts by The following examples illustra e e pre 11 1 welght of dlmethylsfloxy g p p 100 parts y Example 1 weight of the siloxane groups in the copolymer B Using the short term test at room temperature, one 15 Blswelta'ammobutyl)tetramethyldlslloxfme A gram of an ethanol solution containing parts by weight N beta F Y y g a amlnopropyltrlof the indicated inhibitors per 100 parts by weight of ethoxysllane A ethanol was added to millilitersof distilled water in N galjnma ammopropy1 delta ammobutylmeth a beaker. A strip of freshly scoured carbon'steel was oxysllane' A immersed in the solution and tested as described above. 20 N betacyanoethyl deltaamlnobutyltrlethoxysll- Table I below lists results recorded for the inhibitor tested. ane B The results show the improvement resulting from the dlcflrbethoxyethyl gamma alnlnopmpyltrl' practice of this invention. N ethoxysflane TABLE I one Inhibitor: Rating 2 Example III Delta-aminobutylmethyl cyclic tetramer A A copolymer containing 10 parts by weight of gam- The ZOO-hour corrosion test was employed in this exma-aminopropylmethylsiloxy groups and 90 arts periment. In these tests delta-aminobutyltriethoxysilane by weight of dimethylsiloxy groups per 100 parts was used as an inhibitor in several different heat transfer by weight of the siloxane groups in the copoly- 30 liquids. The test fluid systems and results obtained are mer (M. Wt. 30,000) B given in Part I of Table III below. In Part II of Table I N D III, the efiectiveness of delta-aminobutyltriethoxysilane is Exam 18 H compared directly with a typical organic amine inhibitor p (triethanolamine) in aqueous ethylene glycol to show the Using the short term test at room temperature, oneunexpected improvements in corrosion inhibition obtained tenth gram (0.1 g.) of each of the indicated inhibitors with delta-aminobutyltriethoxysilane. There are two runs used in this invention was added to 10 milliliters of ethwith each system. The results show that this invention is ylene glycol. This mixture was then diluted with 20 milliapplicable to the protection of a wide variety of metals liters of water containing 100 p.p.m. each of chloride, that come in contact with a wide variety of liquids.

TABLE III Corrosion wt. loss, mg./9 sq. in. 3 Amount of Liquid 1 Inhibitor inhibitor 2 Fe Al BR Cu PART I Distilledwater De1taaminobutyltriethoxysllane. 0.3 93 4 7 Do N n 1,169 .3 7s 27 parts methanol, 73 parts water Deli:a-aminobutyltriethoxysi]ane. 0. 27 338 14 4 6 D0 one 436 23 11 53 5% aqueous, NaCl snlutinn Delta-aminobutyltriethoxysilane. 0. 3 328 386 74 41 Do None 299 681 119 427 33 parts dimethylsull'oxide, 67 parts Dalta-armnobutyltriethoxysilane- 0.33 21 5 4 5 35 N 632 42 69 33 parts propylene glycol, 67 parts Delta-aminobutyltriethoxysilane- 0.33 100 26 4 3 i)? None 974 77 237 215 33 parts ethylene glycol, 67 partswater- Delta-aminobutyltriethoxysilane. 0.33 41 11 3 6 Do None--- 1,739 40 196 186 PART II v 33partsethylene glycol, 67partswater Triethanolamine 0.25 555 833 176 V 1 Parts by volume per parts by volume of the liquid. 2 Parts by weight per 100 parts by weight of liquid. 3 Average of two runs.

: *parts by weight of water and glycol. A strip of freshly scoured carbon steel was immersed in the solutions and The inhibitors low. The results show that good protection is obtained when any of the Wide variety of organosilicon inhibitors containing a group represented by Formula 1 are used in this invention.

Example IV 70 tionality. The test data is tabulated-in Table IV. With the exception indicated in the table, the liquid contained 0.33 part by Weight of the inhibitor per 100 parts by weight of a liquid obtained by mixing 33 parts by volume of ethylene glycol and 66 parts by volume of water. The

75 data recorded is an average of two test runs. 'The results 1 I show that good protection is obtained with organosilicon inhibitors of different functionality containing a group represented by Formula 1.

1 2 Example VI The ZOO-hour corrosion test was employed to test liquids containing polymeric inhibitors used in this in- TABLE VI pH 6 RA 1 Corrosion, mg. per 9 sq. in. Inhibitor 5.8.

I F 1 F Fe Al BR Cu 9.2 12 15 16 8 5.5 [NH2 H2)a 1.sl 10.3 9,2 as 8 26 10 12 5 q immunis d] 10.3 3g 1 l3 l3 3; 2 2 2;? [NHz(CH2)3SiO1.5] 9. 4 7 52 5 8 11 5 ntrusions. l 9.4 i 12 i 7 70 1 7 a s [NH2(C Hz)3SlO1.5]

9 5 9.7 7 13 5G 1 7 10 5.5 ofinssiotnu 9.7 11 74 1 4 5 5.5 l -fl m l 14 g i g g rNnxonnsio .51 26 4 v4 4 5.5 onlsomi .i 21 l 34 s 4 a e iNmwHflxsiol-l l .2 l 1%. a a 2 z 2 9.9 16 22 2 5 4 5 l zw zh gmli 19g 8 17 219 2 6 4 5 [NH2(CH2)sSi 1.5 2 47 105 12 1s 5 [McSiOm] m1 7.7 l 14 l 2 10s 48 9 20 5 4 Solder spot rating.

5 Copolymer composed of twice as many NH2(CH2)3SiO1.5 groups as MeSiOm groups; 1.0 parts by weight vention. The test liquids contained 0.33 part by weight of the indicated inhibitor per 100 parts by weight of a solution formed by mixing 33 parts by volume of ethylene glycol and 66 parts by volume of water. The test results are tabulated on Table VI. The test data show that the polymers provided excellent protection. The homopolymers were somewhat better in protecting iron, whereas the copolymers were markedly better in protecting aluminum.

Example VII Liquids that had been treated according to the process of this invention were stored for five month's, both at room temperature and at 50 C. At the end of the storage period the compositions were inspected to determine if any change in color had occurred and if any precipiof inhibitor used in this run.

I is initial value and F is final value.

TABLE IV Corrosion, mg. wt. loss/9 sq. in.

Inhibitor Fe Al B R Cu Gamma-aminopropyltriethoxysilane 38 4 6 Gamma-aminopropylpolysiloxane 39 155 12 38 Gamma-aminopropylrnethyl cyclic siloxanes (mixture) 62 165 14 36 Gamma-aminopropylmethyl siloxane cyclic tetramer 26 206 7 11 Delta-aminobutyltriethoxysilane. 40 11 3 5 Delta-aminobutylrnethyldiethoxysilane 38 47 5 6 Delta-aminobutylmethyl cyclic tetramer 13 51 6 7 Epsilon-arninopentyltriethoxysilane 42 5 3 4 Beta-aminophenylethylmethyldiethoxysilane 439 103 8 10 None 1, 739 40 196 186 0.66 part by weight per 100 parts by weight of the liquid inhibitor used in this experiment.

Example V The 200-hour corrosion test was employed to show resistance to corrosion afforded by the secondary and tertiary amines used as inhibitors in this invention and a comparison of such amines with a primary amine used in this invention as inhibitors. The results of these tests are described in Table V below. It will be noticed from these tests that, although secondary and tertiary amines perform satisfactorily, inhibition generally seems to decrease as N-substitution is increased. Tests were run with liquids containing 0.33 part of weight of inhibitor per 100 parts by weight of a liquid produced by mixing 33 parts by volume of ethylene glycol and 67 parts by volume of water. The results are average of two runs.

TABLE V Corrosion, mg. wt. loss/9 sq. in. Inhibitor Fe A1 13 It On NII2(CH2)3Sl(OC2Hb)3 38 25 4 6 021150OCC2I 4NII(CH2)3Sl(OC2H5)3- 415 193 135 G9 (C2H5OO(102114)2N(CHz)zSi(OC2Hr)a 445 191 165 153 HgNC H NH(CI-I2)4Si(OCgH5)a- 36 154 10 None 1, 739 196 I86 tates had formed. The results are shown on Table VII. The results demonstrate the good shelf life of such liquids. No precipitate was observed in the tests.

Parts by weight per parts by weight of a liquid obtained by mixing 33 parts by volume of ethylene glycol and 66 parts by volume of water.

Example VIII Solutions of ethylene glycol and water (obtained by mixing 33 parts by volume of ethylene glycol and 66 parts by volume of water), with and without an inhibitor, were tested in the cooling system of a Ford V-8 engine in a test car. The car was used in normal operation. Weighed strips of copper, aluminum and iron and a brass coupon on which was a spot of solder were immersed in the coolant. At the end of the test the strips were cleaned and reweighed. The water used contained 100 p.p.m. each of chloride sulfate and bicarbonate ions. Samples of the liquids were withdrawn and analyzed during the test. The results appear in Table VIII. Good protection was also afforded iron, copper and solder by the inhibitor. The inhibited solution maintained a pH over 7 and good reserve alkalinity.

TABLE VIII TABLE X Test Inhibited solution Uninhibited solution pq of Weight loss Percent miles (mg/4.5 sq. in.) (mg/4.5 sq. in.) inhlbltvrl Ofsteelz proteetwna aluminum aluminum 5 None 113 4 27 4 9 0. 5 58 48. 5 6, 04 9 118 1. 56 50.

1 1 part by weight of delta-aminobutyltriethoxysilane per 100 parts by l Parts b Weight per 100 parts by weight of weight of the glycol. field Solutlon- 2 Average of two runs in gm. per sq. cm. Example IX 3 Percent protection= X100 Solutions of ethylene glycol and water (obtained by E 1 X1 mixing 33 parts by volume of the glycol and 66 parts xamp e by volume of water) with and without an inhibitor, were 15 The corrosion inhibiting properties of an inhibitor used tested in the cooling system of a Ford V-8 engine in a in this invention [NH (CH Si(OC H were tested. test car that was used 1n normal operat1on. Weighed The ZOO-hour corrosion test was used except for one run str1ps-of copper, alummum and non and a brass coupon where instead of aerating the test solution, argon was on Which Was a spot f ld r W re Imm rsed 1n th 3001- bubbled into the system to simulate actual conditions since ant. At t nd f t t st t s p Were Cleaned and 2 in actual use of such solutions little air might be availl'ewelghed- The Water used Contained 100 P-P- w able. The results obtained are shown on Table XI. Exof chloride, sulfate and b1carbonate ions. Samples of cellent iron, copper and brass protection was obtained in the solutions were analyzed. The results appear in both runs.

. TABLE XI pH RA Wt. losses, mg./9 sq. in. yp Amount 1 8.8.

I F I F Fe Al BR Cu NH (CH )4Si(OEt) (not 9.5 s 3 s7 3 4 6 aeiatedf argon atmosphere) {9.5 14 l 9 3 94 2 4 5 9.8 7 41 15 3 6 0 Nunonmsmonn) 0. 33 10.3 9.7 1a 8 8 3 5 6 None 6.9 4.9 0 Acid 1, 739 40 190 186 4.5

1 Parts by weight per 100 parts by weight of a liquid obtained by mixing 33 parts by volume of ethylene glycol and 66 parts by volume of water.

Tables lX-A and IXB and show the marked improvement in iron protection resulting from the practice of this 1 invention.

TABLE IXA.SOLUTION ANALYSIS Experimental formula 1 Uninhibited water glycol solution Test mileage pH RA pH BA TABLE LXB.CO RROSION Experimental formula 1 Uninhibited water wt. loss, lug/4.5 sq. in. glycol solution wt. loss, Test mileage mg./4.5 sq. in.

Fe Al Cu 8.8. Fe Al Cu S.S.

1 1 partlby weight of HzN(OHz)4Si(OCgH5)3 per 100 parts by weight of I the glyc Example X Example XII The effect of varying the amount of inhibitor used in this invention was investigated, using the ZOO-hour corrosion test. The liquid used was obtained by mixing the 33 parts by volume of ethylene glycol and 66 parts by volume of water. The results obtained are shown on Table XII. The results show that good corrosion protection is obtained over a wide range of inhibitor concentrations.

TABLE XII [A. Deltaraminobutyltriethoxysilane] pH RA Wt. losses, mg./9 sq. in. Amount of 5.8. inhibitor I F I F Fe Al BR Cu 7.5 0 sis 135 '58 e1 5 a ll 2 s3 it t a 2 2 O 12-2 .2 a a i a 6 e 1.5 10.7 8% 1s 2g i 1,1,

. 4 a 2-2 a 2 1t 5% 5 M {9.7 l i s 20 7 12 a [B. Deltasaminobutylmethylsiloxane cyclic tetramer] 6.7 0 395 30 03 49 5 ls-2 2 .2 a :2 2 t a.

. 2 5 10 5 it-i t a t 2 5 iti 2; 2 a: s 7 9 v5 {10.5 l 66 7 195 15 11 5% 1 Parts by weight of the inhibitor per parts by weight of the glycol Example XIII A solution was formed containing 1.0 g. of

cc. of ethylene glyol and cc. of water containing 100 parts per million each of chloride, sulfate and bicarbonate ions. A strip of freshly scoured carbon steel (strip A) was immersed in the solution and the solution was aerated rapidly for 24 hours. A similar steel strip (strip B) was immersed in a similar solution containing 10 no inhibitor and the solution was aerated rapidly for 24 hours. At the end of the test strip A was found to be bright over most of its surface area whereas strip B appeared to be seriously rusted over most of its surface area. Both strips were then gently scoured to remove rust and then weighed. Strip A was found to have undergone a weight loss of 0.05% whereas strip B had had a weight loss of 0.13%.

Example XIV A solution was formed containing 10 cc. of ethylene glycol, 20 cc. of water containing 100 parts per million each of sulfate, chloride and bicarbonate ions and 0.1 g. of a siloxane copolymer. The siloxane copolymer was an oil composed of 35 parts by weight of N,N-di(beta- 25 hydroxyethyl)-delta-aminobutylmethylsiloxy group [i.e. (HOCH CH N(CH SiMeO groups] and 65 parts by weight of dimethylsiloxy groups per 100 parts by weight of the siloxane groups in the copolymer. A strip of freshly scoured carbon steel (strip A) was immersed in this solution and the solution was aerated for 24 hours.

A similar steel strip (strip B) was immersed in a similar solution containing no inhibitor that was also aerated for 24 hours. Both strips were then scoured gently to remove the rust and weighed. Strip A had had a weight loss of 0.11% whereas strip B had had a Weight loss of 0.19%.

Example XV A mixture was formed containing 25 cc. of water that contained 100 parts per million each of chloride, sulfate and bicarbonate ions and 0.1 gram of a hydroxy-endblocked delta-aminobutylmethylpolysiloxane [i.e. HO (NH (CH SiMeO) H] that had a viscosity of 537 centipoises and that contained 4 parts by weight of hydroxyl groups per 100 parts by weight of the siloxane. A strip of freshly scoured carbon steel (strip A) was immersed in the mixture and the mixture was aerated for 24 hour. A similar steel strip (strip B) was immersed in water containing the same ions but no inhibitor and the water was aerated for 24 hours. Both strips were then scoured gently to remove rust and weighed. Strip A had had a weight loss of 0.15% whereas strip B had had a weight loss of 0.77%.

Example XVI Solutions containing the indicated organosilicon inhibitors were evaluated in the ZOO-hour corrosion test. The solution contained 100 parts by weight ethylene glycol and 180 parts by weight water. The results are shown on Table XIII. The results demonstrate the effectiveness of the organosilicon inhibitors in retarding corrosion, es pecially the corrosion of aluminum.

Other organosilicon inhibitors that are useful in the process of this invention are N-beta-aminoethyltrimethoxysilane, N-gamma-aminopropyltrimethoxysilane, beta- (p-aminomethylphenyl)-ethyl-triethoxysilane and the alkoxycontaining amino-organosiloxanes produced by the partial hydrolysis and condensation of any of these silanes.

What is claimed is:

1. A process for inhibiting the corrosion of a metal selected from the group consisting of magnesium and the metals below magnesium in the electromotive series that come in contact with a corrosive aqueous liquid selected from the group consisting of water having dissolved therein inorganic solutes and water having dissolved therein water-soluble organic compounds, which process comprises providing in the corrosive liquid a corrosion inhibit ing amount of an organosilicon compound selected from the group consisting of (I) silanes represented by the formula:

R55 Z NRiXbb-l wherein:

(a) Z is a member selected from the group consisting of the hydrogen atom, the monovalent hydrocarbon groups, the substituted monovalent hydrocarbon groups containing a substituent selected from the group consisting of the amino, hydroxyl, amido, ester, cyano and hydrocarbonoxy groups and divalent groups that are derived from oxirane compounds by the opening of the oxirane ring and that link the nitrogen atom to the silicon atom through a carbon to carbon to oxygen linkage;

(b) R is a divalent hydrocarbon group containing at least three carbon atoms;

(c) the Z N- group is attached to at least the third carbon removed from the silicon atom;

(d) R is a member selected from the group consisting of the monovalent hydrocarbon groups and the H NC H groups where n has a value of at least three;

(e) b has a value from O to 2;

(f) f has a value from O to 2 and represents the number of said divalent groups represented by (g) 3b-f has a value from 1 to 3; and

(h) X is a member selected from the group consisting of the alkoxy and aroxy groups;

(II) siloxanes consisting essentialy of siloxane groups represented by the formula:

wherein:

(a) Z is a member selected from the group consisting of the hydrogen atom, the monovalent hydrocarbon groups and the substituted monovalent hydrocarbon groups containing a substituent selected from the group consisting of TABLE XIII pH RA Wt. losses (mg/9111. Organosilicon Compounds Amount 1 8.5.

I F I F Fe Al BR Cu rn-NH CIIzCaHrsfloC Hm 1.0 9.7 9.6 13 5 37 1 3 l 5 9.7 6 39 2 4 0 5 NHZC2H4 1VIQ CHZSI(OCZII5)2NH2 1.0 11 {10.6 05 17 14 1 2 3 5.5 C 2 s 10.6 20 9 1 2 2 5.5 pNHZH2C6H4Si(OC2II5)3 1.0 9.4 9.8 14 8 81 0 2 3 5 9.7 8 63 0 1 1 5 1 Parts by weight per parts by weight of the aqueous glycol.

17 amino, hydroxyl, amido, ester, cyano and hydrocarbonoxy groups; (b) R is a divalent hydrocarbon group containing at least three carbon atoms; (c) the Z' N group is attached to at least the third carbon removed from the silicon atom; (d) R is a member selected from the group consisting of the monovalent hydrocarbon groups and the H NC H groups where n has a value of at least three; and (e) b has a value from 0 to 2; and (III) siloxanes consisting essentially of both (1) the above-defined siloxane groups and (2) groups represented by the formula:

lwsio wherein R is a monovalent hydrocarbon group and c has a value from 1 to 3. Y

2. The process of claim 1 wherein the corrosive aqueous liquid is water having dissolved therein inorganic solutes and wherein the inorganic solute contains sulfate ions.

3. The process of claim 1 wherein the corrosive aqueous liquid is water having dissolved therein inorganic solutes and wherein the inorganic solute contains bicarbonate ions.

4. The process of claim 1 wherein the organosilicon compound is N-beta-aminoethyl-gamma-aminopropyltriethoxysilane.

5. A process for inhibiting the corrosion of iron that comes in contact with corrosive water containing chloride ions, which process comprises providing in the water a corrosion inhibiting amount of an alcohol-soluble silane represented by the formula:

(a) Z is a member selected from the group consisting of the hydrogen atom, the monovalent hydrocarbon groups, the substituent monovalent hydrocarbon groups containing a substituent selected from the group consisting of the amino, hydroxyl, amido, ester cyano and hydrocarbonoxy groups and divalent groups that are derived from oxirane compounds by the opening of the oxirane ring and that link the nitrogen atom to the silicon atom through a I carbon to carbon to oxygen linkage;

(b) R is a divalent hydrocarbon group containing at least three carbon atoms;

(c) the Z N group is attached to at least the third carbon removed from the silicon atom;

(d) R is a member selected from the group consisting of the monovalent hydrocarbon groups and the H NC H groups Where n has a value of at least three;

(e) b has a value from 0 to 2;

(f) f has a value from 0 to 2 and represents the number of said divalent groups represented by Z;

(g) 3bf has a value from 1 to 3; and

(b) X is a member selected from the group consisting of the alkoxy and aroxy groups, said silane being soluble in said corrosive water.

6. A process for inhibiting the corrosion of aluminum that comes in contact with corrosive water containing chloride ions, which process comprises providing in the water a corrosion inhibiting amount of a siloxane consisting essentially of groups represented by the formula:

wherein:

(a) Z is a member selected from the group consisting of the hydrogen atom, the monovalent hydrocarbon groups, the substituent monovalent hydrocarbon groups containing a substituent selected from the group consisting of amino, hydroxyl, amido, ester, cyano and hydrocarbonoxy groups;

(b) R is a divalent hydrocarbon group containing at least three carbon atoms;

(c) the Z' N group is attached to at least the third carbon removed from the silicon atoms;

(d) R is a member selected from the group consisting of the monovalent hydrocarbon groups and the H NC H where n has a value of at least three; and

(e) b has a value from 0 to 2, said siloxane being soluble in said corrosive water.

7. A process for inhibiting the corrosion of aluminum that comes in contact with corrosive water containing chloride ions, which process comprises providing in the water a corrosion inhibiting amount of a siloxane consisting essentially of groups represented by the formula:

wherein: (a) Z is a member selected from the group consisting of the hydrogen atom, the monovalent hydrocarbon groups and the substituted monovalent hydrocarbon groups containing a substituent selected from the group consisting of amino, hydroxyl, amido, ester, cyano and ,hydrocarbonoxy groups; i

(b) R is a divalent hydrocarbon group containing at least three carbon atoms;

(c) the Z N group is attached to at least the third carbon removed from the silicon atoms;

(d) R is a member selected from the group consisting of the monovalent hydrocarbon groups and the H NC H where n has a value of at least three; and

(e) b has a value from 0 to 2 and groups represented by the formula:

wherein R is a monovalent hydrocarbon group and c has a value from 1 to 3, said siloxane being soluble in said corrosive water.

8. A process for inhibiting the corrosion of a metal selected from the group consisting of magnesium and the metals below magnesium in the electromotive series that come in contact with corrosive water containing chloride ions, which process comprises providing in the water a corrosion inhibiting amount of an alcohol-soluble siloxane consisting essentially of groups represented by the formula:

R55 Z QNRS iO3 b T wherein:

(a) Z is a member selected from the group consisting of the hydrogen atom, the monovalent hydrocarbon groups and the substituted monovalent hydrocarbon groups containing a substituent selected from the group consisting of amino, hydroxyl, amido, ester, cyano and hydrocarbonoxy groups;

(b) R is a divalent hydrocarbon group containing at least three carbon atoms;

(0) the Z N- group is attached to at least the third carbon removed from the silicon atoms;

(d) R is a member selected from the group consisting of the monovalent hydrocarbon groups and the H NC H wherein n has a value of at least three; and

(e) b has a value from to 2, said siloxane being soluble in said corrosive water.

9. A process for inhibiting the corrosion of a metal selected from the group consisting of magnesium and the metals below magnesium in the electromotive series that come in contact with corrosive water containing chloride ions, which process comprises providing in the water a corrosion inhibiting amount of an alcohol-soluble siloxane consisting essentially of both (1) groups represented by the formula:

wherein:

(a) Z' is a member selected from the group consisting of the hydrogen atom, the monovalent hydrocarbon groups and the substituted monovalent hydrocarbon groups containing a substituent selected from the group consisting of amino, hydroxyl, 'amido, ester, cyano and hydrocarbonoxy groups;

(b) R is a divalent hydrocarbon group containing at least three carbon atoms;

(0) the Z N group is attached to at least the third carbon removed from the silicon atoms;

(d) R is a member selected from the group consisting of the monovalent hydrocarbon groups and the H NC H where n has a value of at least three; and

(e) b has a value from 0 to 2; and

(2) groups represented by the formula:

R SiO wherein R is a monovalent hydrocarbon group and c has a value from 1 to 3, said siloxane being soluble in said corrosive water.

10. A process for inhibiting the corrosion of iron that comes in contact with corrosive water containing an organic solute which comprises adding to the water from .0001 part to 10 parts by weight of a siloxane consisting essentially of gamma-aminopropylsiloxy groups per parts by weight of water.

11. A process for inhibiting the corrosion of aluminum which comes in contact with corrosive water containing an organic solute which comprises adding to the Water from .0001 part to 10 parts by Weight of a siloxane consisting essentially of delta-aminobutylsiloxy groups per 100 parts by weight of water.

12. A process for inhibiting the corrosion of iron which comes in contact with corrosive Water containing an organic solute which comprises adding to the water from .0001 part to 10 parts by weight of gamma-aminopropyl- (methyl)siloxane cyclic tetramer per 100 parts by weight of Water.

13. A process for inhibiting the corrosion of iron which comes in contact with corrosive water containing an organic solute which comprises adding to the water from .0001 part to 10 parts by weight of gamma-aminopropyltriethoxysilane per 100 parts by weight of Water.

References Cited by the Examiner UNITED STATES PATENTS 2,715,133 8/1955 Speier 260448.2 2,762,823 9/1956 Speier 260448.2 2,833,802 5/1958 Merker 252-389 2,881,184 4/1959 Pike 260448.2 2,926,108 2/1960 Anderson 2528.55 3,017,353 1/1962 Jewell 2528.55 3,069,451 12/1962 Fritz 260448.2 3,085,908 4/1963 Morehouse et al. 260448.2

JULIUS GREENWALD, Primary Examiner. 

1. A PROCESS FOR INHIBITING THE CORROSION OF A METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM AND THE METALS BELOW MAGNESIUM IN THE ELECTROMOTIVE SERIES THAT COME IN CONTACT WITH A CORROSIVE AQUEOUS LIQUID SELECTED FROM THE GROUP CONSISTING OF WATER HAVING DISSOLVED THEREIN INORGANIC SOLUTES AND WATER AND HAVING DISSOLVED THEREIN WATER-SOLUBLE ORGANIC COMPOUNDS, WHICH PROCESS COMPRISES PROVIDING IN THE CORROSIVE LIQUID A CORROSION INHIBITING AMOUNT OF AN ORGANOSILICON COMPOUND SELECTED FROM THE GROUP CONSISTING OF (I) SILANES REPRESENTED BY THE FORMULA 